The present invention is directed to a double wall, flexible hose which has an inside wall surface spaced from an outside wall surface with a helical reinforcement with axial spacing between the turns being positioned in a cavity between the walls and to the method of manufacturing the hose.
Hoses that are provided with armoring or support helixes in order to prevent the hose for collapsing are frequently employed for suction and/or partial vacuum systems. Such hose designs are in fact light and flexible. However, the undulatory outside contour caused by the supporting helix is disadvantageous and raises problems with respect to cleanliness. This is especially true in the areas of special hygienic demands, for example, in the medical field. It is difficult, if not even impossible, to keep an undulatory surface faultlessly clean on a permanent basis.
In order to overcome these drawbacks, attempts have already been undertaken as disclosed in Austrian Letters Pat. No. 239019. As disclosed, the hose is provided with a smooth wall on the inside wall surface and the outside is provided with a cover hose such as a second outside skin that has been extruded or, respectively, drawn over the undulatory outer contour of the inside hose structure. While largely retaining the flexibility, a relatively smooth outer contour can in fact be achieved with such a hose reinforcement. However, such a construction for a hose continues to exhibit the slightly undulatory contours typically given such helical hoses together with the aforementioned disadvantages of poor cleanability and hygienics of the surface.
A hose design is also disclosed in German GM 8012326 wherein inner and outer continuous hose jackets or sleeves are disposed concentric to each other and spaced apart by a reinforcing helix which is connected between the two hose jackets. This hose design is difficult to manufacture insofar as the hose consists of individual components comprising the inside sleeve, a helix and an outside sleeve that must be separately manufactured and connected to one another. This produces an extensive and expensive apparatus outlay. In addition, a good, mutual connection of the individual components is very difficult due to the chronological and special staggered manufacturing process of the individual components. The contour of the outer hose is also slightly undulatory in this instance in order to still be able to achieve a relatively good flexibility given the relatively short intervals and axial directions between the turns of the support helix.
A synthetic pipe, which is principally designed for underground installation as well as a method for manufacturing this pipe, is disclosed in Belgian Pat. No. 565101. In this patent, a synthetic pipe is manufactured by means of helically wrapping one or more tapes of semifluid yet relatively stiff material. Internally disposed, helically extending cavities that lend the respective rigid pipe a certain flexibility, are created by means of the wrapping of the tapes. The pipe thus remains stable in shape given external acting loads such as from the earth surrounding the hose or pie, but is somewhat yielding within narrow limits. In order to make the pipe more resistant to pressure and radial expansion, the cavities can either be filled with air which means that the air chambers must be closed or with a material that is even stiffer in comparison to the material of the tapes of the pipe, for example, asbestos, cement or polyester fiberglas or the like.